Wikipedia
Riigihoidja (officially translated as President-Regent) was the name of the office of the head of state and head of government of Estonia from 3 September 1937 to 24 April 1938. The only person to hold this position was Konstantin Päts, five time former State Elder. His eventual successor ex officio was Johan Laidoner, then Commander-in-Chief.
According to the Constitution of the Republic of Estonia Amendment Act, initiated by the citizens initiative and approved by the people on the referendum on 14, 15 and 16 October 1933, (Riigi Teataja 28 October 1933 No. 86 Article 628) which entered into force on the 100th day after the referendum of 24 January 1934, the Elder of State was the representative of the people who executed the highest administrative power in the State. For governing the State, there was by the Elder of State the Government of the Republic (Section 57) appointed by the Elder of State and chaired by the Prime Minister (Section 64). By the Resolution No. 173 from 12 March 1934 (Riigi Teataja 16 March 1934 No. 22 Art 56), Konstantin Päts extended validity of martial law to the whole territory of state for 6 months, which was later prolonged. During the martial law, the elections of the Elder of State were not organised and Konstantin Päts the Prime Minister acted as the Elder of State.
In accordance with the Period of Transition Act, which was proclaimed on 17 August 1937 by Konstantin Päts as Prime Minister in duties of the Elder of State, and entered into force on 3 September 1937 after publication in the Riigi Teataja (3 September 1937 nr 71 art 598) the Prime Minister continued to fulfil his duties in the official status of the Protector of State in duties of the Elder of State until the new Riigikogu had been convened.
He was also his own successor as first President from 24 April 1938 until 23 July 1940, formally until shortly after Soviet troops had occupied Estonia in June 1940.